I just had new tile put in my bathroom. They cut off the old corroded cast iron flange, laid a new piece of plywood over the old, did a new mortar floor, and laid the hex tile. They cut the pipe low so the entry to the cast iron pipe entry sits about 2" below the tile. I planned to use the Oatey 43539 repair flange which reaches the pipe just fine. My problem is the pipe and flange s not concentric to the holes in the plywood. Therefore I don't have a good surface to fasten the new flange to. Should I just screw into the tile and mortar with long screws? Does it make more sense to block in some new plywood from underneath tight to the pipe, break out the tile and mud so I can put in wood spacers, set the flange on that (level with the floor) and screw it all together? Do you have better recommendation altogether?